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Indicator Assessment
Projected change in river floods with a return period of 100 years
Note: 100-year daily peak flow (Q100). Relative change for the time slices 2006-2035, 2036-2065 and 2066–2095 compared to the ensemble mean of the baseline (1976–2005), based on an ensemble of EURO-CORDEX RCP8.5 scenarios. Data points with CV>1 are greyed out. (CV = coefficient of variation)
Past trends
Figure 1 shows that the number of very severe flood events in Europe increased over the period 1980–2010, but with large interannual variability. The underlying data is obtained from a combination of information available in global databases such as the Dartmouth Flood Observatory ([1]) and the Emergency Events Database (EM-DAT) of the Centre for Research on the Epidemiology of Disasters (CRED) ([2]), data reported by EU Member States under the EU Floods Directive and an additional country consultation in all EEA member and cooperating countries [i]. Less extreme events or events with small spatial extent are not included, but the combination of data sources still leads to a large improvement over an overview based on global data sources only. Furthermore, selection of ‘larger’ floods only (here with severity class ‘very high’) is expected to reduce the reporting bias [ii]. For comparison, the NatCatSERVICE database in total contains more than 1 200 flood events that have happened since 1990, which, on average, is over 50 per year.
Losses from flooding in Europe have increased substantially since the 1970s [iii]. In recent years, some flood events have been so much stronger than previous events that they have led to significant changes in flood risk estimation methods for that region, e.g. in the United Kingdom [iv]. The trend for increasing losses from river floods is primarily attributable to socio-economic factors, such as increasing wealth located in flood zones, but increases in heavy precipitation in parts of Europe may also play a role. Robust attribution is not yet possible because of insufficient data [v]. In terms of regional GDP, flood risks are highest in large parts of eastern Europe, Scandinavia, Austria and the United Kingdom and parts of France and Italy [vi]. A shift from a purely technically oriented flood defense toward a more integrated flood risk management system that also considers nonstructural measures to minimize adverse effects of flooding has led to more effective flood management and to a reduction of damage caused by the 2013 floods in Germany, compared to the 2002 floods [vii].
Projections
Future changes in the risk of river floods in Europe have been simulated using a hydrological model driven by an ensemble of climate simulations [viii]. Of particular interest is the frequency analysis of flood peaks above the 100-year flood level, which is the average protection level of the European river network (albeit with significant differences) [ix].
Figure 2 shows the change in the level of one-in-a-century (Q100) floods between the reference period and three future time periods based on the hydrological model LISFLOOD and an ensemble of seven climate models [x]. Blue rivers indicate an increase in flood level and red rivers indicate a decrease. For the end of the 21st century, the greatest increase in Q100 floods is projected for the British Isles, north-west and south-east France, northern Italy and some regions in south-east Spain, the Balkans and the Carpathians. Mild increases are projected for central Europe, the upper section of the Danube and its main tributaries. In contrast, decreases in Q100 floods are projected in large parts of north-eastern Europe owing to a reduction in snow accumulation, and hence melt-associated floods, under milder winter temperatures. These results are consistent with earlier studies [xi]. While the ensemble mean presented in Figure 2 provides the best assessment of all model simulations together, individual simulations can show important differences from the ensemble mean for individual catchments. This is partly the result of significant decadal-scale internal variability in the simulated climate [xii]. Furthermore, the LISFLOOD analysis is restricted to the larger rivers in Europe, which may not be representative of a whole country or region. For example, in northern Europe, rainfall-dominated floods in smaller rivers may increase because of projected increases in precipitation amounts, even where snowmelt-dominated floods in large rivers are projected to decrease [xiii].
Changes in flood frequencies below the protection level are expected to have less significant economic effects and affect fewer people than even small changes in the largest events (e.g. with a return period of 500 years). For a number of European river basins, including the Po, Duero, Garonne, Ebro, Loire, Rhine and Rhone, an increase in extreme floods with a return period above 500 years is projected; this includes river basins such as Guadiana and Narva, where the overall frequency of flood events is projected to decline [xiv]. A follow-up study combined the results of this flood hazard assessment with detailed exposure maps to estimate the economic and health risks from river floods in Europe. The results suggest that a high climate change scenario could increase the socio-economic impact of floods in Europe more than three-fold by the end of the 21st century. The strongest increase in flood risk is projected for Austria, Hungary, Slovakia and Slovenia [xv]. A combination of different adaptation measures has been estimated to reduce economic damage from (fluvial and coastal) floods substantially by 67 to 99 % and reduce the number of people flooded by 37 to 99 % for the 100-year event [xvi].
[i] ETC/ICM, ‘Flood Phenomena Database — Structure and Assessment’ (Magdeburg: European Topic Centre on Inland, Coastal and Marine Water, 14 July 2015), http://forum.eionet.europa.eu/nrc-eionet-freshwater/library/floods/country-review-european-floods-impact-database-2015/flood-phenomena-database-structure-and-assessment.
[ii] Zbigniew W. Kundzewicz, Iwona Pińskwar, and G. Robert Brakenridge, ‘Large Floods in Europe, 1985–2009’,Hydrological Sciences Journal 58, no. 1 (January 2013): 1–7, doi:10.1080/02626667.2012.745082.
[iii] J.I. Barredo, ‘Normalised Flood Losses in Europe: 1970–2006’,Natural Hazards and Earth System Sciences 9 (9 February 2009): 97–104, doi:10.5194/nhess-9-97-2009.
[iv] J. D. Miller et al., ‘A Hydrological Assessment of the November 2009 Floods in Cumbria, UK’,Hydrology Research 44, no. 1 (December 2013): 180, doi:10.2166/nh.2012.076; Nathalie Schaller et al., ‘Human Influence on Climate in the 2014 Southern England Winter Floods and Their Impacts’,Nature Climate Change 6 (1 February 2016): 627–34, doi:10.1038/nclimate2927.
[v] Barredo, ‘Normalised Flood Losses in Europe: 1970–2006’; Luc Feyen et al., ‘Fluvial Flood Risk in Europe in Present and Future Climates’,Climatic Change 112, no. 1 (2012): 47–62, doi:10.1007/s10584-011-0339-7.
[vi] Nicola Lugeri et al., ‘River Flood Risk and Adaptation in Europe—assessment of the Present Status’,Mitigation and Adaptation Strategies for Global Change 15, no. 7 (October 2010): 621–39, doi:10.1007/s11027-009-9211-8.
[vii] Annegret H. Thieken et al., ‘Review of the Flood Risk Management System in Germany after the Major Flood in 2013’,Ecology and Society 21, no. 2 (2016): 51, doi:10.5751/ES-08547-210251.
[viii] Rodrigo Rojas et al., ‘Assessment of Future Flood Hazard in Europe Using a Large Ensemble of Bias Corrected Regional Climate Simulations’,Journal of Geophysical Research 117 (2012): D17109, doi:10.1029/2012JD017461; L. Alfieri et al., ‘Global Warming Increases the Frequency of River Floods in Europe’,Hydrology and Earth System Sciences 19, no. 5 (11 May 2015): 2247–60, doi:10.5194/hess-19-2247-2015.
[ix] Rodrigo Rojas, Luc Feyen, and Paul Watkiss, ‘Climate Change and River Floods in the European Union: Socio-Economic Consequences and the Costs and Benefits of Adaptation’,Global Environmental Change 23, no. 6 (December 2013): 1737–51, doi:10.1016/j.gloenvcha.2013.08.006; Brenden Jongman et al., ‘Increasing Stress on Disaster-Risk Finance due to Large Floods’,Nature Climate Change 4, no. 4 (2 March 2014): 264–68, doi:10.1038/nclimate2124.
[x] Alfieri et al., ‘Global Warming Increases the Frequency of River Floods in Europe’.
[xi] e.g. Rutger Dankers and Luc Feyen, ‘Flood Hazard in Europe in an Ensemble of Regional Climate Scenarios’,Journal of Geophysical Research 114, no. D16 (27 August 2009): D16108, doi:10.1029/2008JD011523; J.-C. Ciscar et al., ‘Physical and Economic Consequences of Climate Change in Europe’,Proceedings of the National Academy of Sciences 108, no. 7 (15 February 2011): 2678–83, doi:10.1073/pnas.1011612108; Rojas et al., ‘Assessment of Future Flood Hazard in Europe Using a Large Ensemble of Bias Corrected Regional Climate Simulations’.
[xii] Feyen et al., ‘Fluvial Flood Risk in Europe in Present and Future Climates’.
[xiii] Klaus Vormoor et al., ‘Evidence for Changes in the Magnitude and Frequency of Observed Rainfall vs. Snowmelt Driven Floods in Norway’,Journal of Hydrology 538 (July 2016): 33–48, doi:10.1016/j.jhydrol.2016.03.066.
[xiv] Alfieri et al., ‘Global Warming Increases the Frequency of River Floods in Europe’.
[xv] Lorenzo Alfieri et al., ‘Ensemble Flood Risk Assessment in Europe under High End Climate Scenarios’,Global Environmental Change 35 (November 2015): 199–212, doi:10.1016/j.gloenvcha.2015.09.004.
[xvi] M. Mokrech et al., ‘An Integrated Approach for Assessing Flood Impacts due to Future Climate and Socio-Economic Conditions and the Scope of Adaptation in Europe’,Climatic Change 128, no. 3–4 (4 December 2014): 245–60, doi:10.1007/s10584-014-1298-6.
In April 2013, the European Commission (EC) presented the EU Adaptation Strategy Package. This package consists of the EU Strategy on adaptation to climate change (COM/2013/216 final) and a number of supporting documents. The overall aim of the EU Adaptation Strategy is to contribute to a more climate-resilient Europe.
One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which will be achieved by bridging the knowledge gap and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘one-stop shop’ for adaptation information in Europe. Climate-ADAPT has been developed jointly by the EC and the EEA to share knowledge on (1) observed and projected climate change and its impacts on environmental and social systems and on human health, (2) relevant research, (3) EU, transnational, national and subnational adaptation strategies and plans, and (4) adaptation case studies.
Further objectives include Promoting adaptation in key vulnerablesectors through climate-proofing EU sector policies and Promoting action by Member States. Most EU Member States have already adopted national adaptation strategies and many have also prepared action plans on climate change adaptation. The EC also supports adaptation in cities through the Covenant of Mayors for Climate and Energy initiative.
In September 2016, the EC presented an indicative roadmap for the evaluation of the EU Adaptation Strategy by 2018.
In November 2013, the European Parliament and the European Council adopted the 7th EU Environment Action Programme (7th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7th EAP is intended to help guide EU action on environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7th EAP refer to climate change adaptation.
No targets have been specified.
The number of very severe flood events in Europe is obtained from a combination of information available in global databases such as the Dartmouth Flood Observatory and the Emergency Events Database (EM-DAT) of the Centre for Research on the Epidemiology of Disasters (CRED), data reported by EU Member States under the EU Floods Directive and an additional country consultation in all EEA member and cooperating countries.
Future changes in the risk of river floods in Europe have been simulated using a hydrological model driven by an ensemble of climate simulations. Of particular interest is the frequency analysis of flood peaks above the 100-year flood level, which is the average protection level of the European river network (albeit with significant differences).
Not applicable
Not applicable
The data required for the indicator are river flow (extreme high flows). Time series can be observed or simulated for historical time periods and can be projected for future time windows, taking into account climate change and potentially also other drivers of change, such as land-use changes.
River flow and water level data are influenced by rainfall run-off and by hydromorphological changes of the river bed, e.g. through river engineering. Furthermore, homogeneous time series are generally shorter than those for meteorological data. Therefore, substantially more time may be required before statistically significant changes in hydrological variables can be observed, especially with respect to extreme and exceptional events (floods and droughts). Notwithstanding recent improvements of climate models to simulate large-scale patterns of precipitation and extreme events, projections of changes in precipitation and high extremes remain uncertain, especially at catchment and local scales. Projections of river floods are plagued by the highest levels of uncertainty, as they often depend on changes in single extreme events, whereas changes in average and low-flow conditions depend on changes in precipitation on longer time scales (i.e. monthly to seasonal), which are more robust.
The main data sources for Europe-wide studies of the impacts of extreme hydrological events and their changes are global databases for natural disasters. Recently, the EEA has compiled a European Flood Impact Database that combines information on past floods with significant observed impacts from global sources with the reporting by EU Member States for the Preliminary Flood Risk Assessment (PFRA). This database has been collecting information on flood hazards and their impacts since 1980. At the European level, these inventories could assist in tracking the trends in flood disaster losses and in mitigation programmes, for both monitoring and obtaining a clearer picture of the linkages between climate change, floods and losses from flooding. Also at the European level, guidance for recording and sharing disaster damage and loss data is under development for Europe, coherent with the Sendai Framework for Disaster Risk Reduction.
No uncertainty has been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/river-floods-2/assessment or scan the QR code.
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